\begin{array}
\
\text{sum of the first $1$ elements:} \,\,\,\,\,\,\,\,\,\,\,\,\, h_1 = x_1 \\
\text{sum of the first $2$ elements:} \,\,\,\,\,\,\,\,\,\,\,\,\, h_2 = x_1 + x_2 \\
\text{sum of the first $3$ elements:} \,\,\,\,\,\,\,\,\,\,\,\,\, h_3 = x_1 + x_2 + x_3 \\
\text{sum of the first $4$ elements:} \,\,\,\,\,\,\,\,\,\,\,\,\, h_4 = x_1 + x_2 + x_3 + x_4 \\
\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \vdots \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \vdots \\
\text{sum of the first $t$ elements:} \,\,\,\,\,\,\,\,\,\,\,\,\, h_{t} = x_1 + x_2 + x_3 + x_4 + \cdots + x_t \\
\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \vdots \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \vdots \\
\end{array}